御笠川流域におけるため池の治水効果

抄録

Urban developments cause serious changes to watersheds conditions by decreasing storage area, introducing pavement and channeling. As a result, the peak discharge has been increasing and the arrival time of peak flow becomes early. The purpose of this study is to investigate the state of irrigation ponds in the Mikasa River watershed and to clarify flood control capacity of them. The result of investigation, the catchments area of all irrigation ponds was about 18%, the capacity of flood control was about 450,000m³ in the Mikasa river watershed. For the estimate of the irrigation ponds, we applied the distributed runoff model considering ponds effects about flood disaster in July 19, 2003. The result of calculation showed that the peak discharge at the Sanno Bridge decreased 20m³/s and arrival time of peak flow delayed by the irrigation ponds.